| Abstrakt: |
Standing crop of litter in Yuccabine Creek, an Australian upland rainforest stream, varied from 2.4 ± 0.5 to 11.5 ± 2.7 g dry weight per 1/16 m2, was greatest in the late dry season (October, early summer), and differed substantially between years, because of variations in retention rate rather than in litterfall. Predominant macroinvertebrates in natural litter packs (82% by numbers) were caddis larvae (Trichoptera: Leptoceridae and Calamoceratidae) which appeared to be the main shredders of leaf litter. Rates of litter processing in the stream were estimated using artificial litter packs of single or mixed species and of fresh or aged leaves. Macroinvertebrates accounted for up to 77 % of processing after 64 days (aged leaves), but there was great variation between experiments according to differences in leaf species, pool or riffle environments, and time of year. The most rapid processing resulted in a processing coefficient (—k) value of 0.017, and 50 % decay value (T50) of 32d for fresh leaves of mixed species. For aged leaves (pre-leached) the greatest decay rate produced a T50 value of 32d (the exponential model was inapplicable so —k could not be calculated in this case). The slowest processing (estimated T50 >400d) was for fresh Rhodamnia sessiliflora leaves. There was no apparent relationship between temperature and processing rate in the field, but this result may have been due to a great abundance of litter in summer. The observed variation in the results was caused largely by local factors, such as: leaf species; presence, abundance and distribution of shredders; and the temporal changes in standing crop of litter and abundance of shredders. |
